Using the MAX11209 18bit ADC

Jbeale connected the MAX11209 18 bit ADC to his Seeeduino board and wrote up some test firmware.

The MAX11209 can do 18 bits at sample rates up to 120 Hz (true) or 480 Hz (4x oversampled). It has both external analog and internal digital scaling. There is +Vref and -Vref, as well as +Vin and -Vin, so you can set your own full-range scale and offset via analog voltages (many ADCs have only +Vref, so you can’t set your own analog offset above ground). Maximum Vin = 3.6 V. The data sheet claim that CS/ can be tied low is apparently false (must be brought high after each SPI transaction).
The 11209 is part of a family, some other variants do 24 bits (although there I think some bits will be just noise). With the 11209 I can so far confirm that the input noise is less than 2 uV at a 15 Hz rate. Datasheet claims 0.57 uV RMS at 10 Hz.

Via the forum.

Join the Conversation

1 Comment

  1. One other observation: if you want to use more than one chip at the same time, on a CPU with only one SPI port, I think you have to use the separate-conversions mode (120 Hz max). In continuous mode, you’re supposed to leave the chip selected to wait for DATA/READY to indicate “conversion complete”, because there is a timing hazard on async reads. The only way to really use two or more chips safely in continuous mode is to use an external clock input to both, to guarantee that the conversion timing stays matched.

Leave a comment

Your email address will not be published. Required fields are marked *

Notify me of followup comments via e-mail. You can also subscribe without commenting.